Medical Tricorder to claim the 10 million dollars from The X Prize Foundation.
I'd personally prefer a holodeck sure, but that's for completely self destructive reasons: Go in, never come out.
10 million could set me and my family for life.
There is obviously more profitable choices but I don't know why, I like to tread hypotheticals with a degree of plausibility, as if I'm afraid asking for to much will break the space/time fabric anomaly granting me such an event.
Also on the TARDIS note, I don't care to own a TARDIS (Which I'm sure none of us could operate anyways) I want David Tennant.
Does he count as an item?
If so does he come as a Timelord with his own Sonic Screwdriver and TARDIS?